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Two-thirds of us live within five kilometres of the ocean. Even though scientists predict sea level rise could take decades to affect some coastal communities, water woes have already hit Western Bay neighbours emotionally and financially, as families are told they must leave their homes and ratepayers eye up millions of dollars in potential costs.

Bay of Plenty Times Weekend reporter Dawn Picken talked with local officials and residents to learn how we're preparing for extreme weather and swelling seas.

Waterfront Paradise

Paora Maxwell left corporate life in Auckland for the sweet life in Pukehina Beach 18 months ago. His two-level home perches above the beach, connected to sand by two sets of steep wooden stairs.

There's evidence of erosion control measures on the neighbour's hill, where tyres are embedded in dunes. The view is expansive, featuring Maketu cliffs to your left, and Moutohora (Whale Island) to your right, out at sea.

Pukehina Beach is essentially a long sandspit that forms the northern edge of Waihi Harbour. And it's one of several places in the Western Bay where coastal hazard maps show homes have been built in areas susceptible for natural risks like flooding and erosion over the next 50-100 years.

Understanding the Risk

In Tauranga, more than 1200 homes lie less than 1.5m above the spring tide mark, making them susceptible to rising seas, according to a 2015 Ministry for the Environment study. The research showed 107 businesses and 35km of roading would also be affected.

Most of Tauranga's low-lying homes were in Mount Maunganui, Otumoetai and Matua. Low-lying businesses were near Tauranga Airport.

Research found the Western Bay of Plenty region needed to prepare for sea level rise of 1m over the next 100 years. Rising oceans exacerbated three types of coastal hazards - flooding, erosion and groundwater, which could rise too high or become saline.

Erosion is a natural process, but it has increased due to human impacts and climate change, which have increased sea levels and extreme weather events.

The Bay of Plenty Regional Council is conducting new research in partnership with Tauranga City Council, Western Bay of Plenty District Council and Bay of Plenty Civil Defense to learn how sea level rise impacts the inner harbour through erosion and inundation, as well as on the open coast. The study uses technical information released by the Ministry for the Environment (MFE) in late 2017.

A TCC spokeswoman says gaps were found in groundwater monitoring sites around harbour margins, so council has installed more monitoring locations.

"This will allow landowners, subdividers and developers to utilise this existing information in understanding the groundwater table, generally, when considering development proposals."

Bay of Plenty Regional Councillor Stuart Crosby says a lot of work has been done around natural hazard issues the past couple years.Photo/File.

Once work is finalised, TCC will consider how sea level rise may impact the groundwater table. Findings are expected at the end of this quarter or the beginning of next.

Global Issue

The MFE says average relative sea level rise for the 100 years up to 2015 was around 1.8 millimetres a year. What was an extreme high tide level in 1900 is now reached about twice as often. While projections of rising seas are usually global, MFE said corrections must be made in New Zealand for ocean response and vertical land movement.

An Intergovernmental Panel on Climate Change (IPCC) report in 2013 said sea-level rise in our region is expected to be up to ten per cent more than the global average. IPCC says future warming will cause rising seas due to expansion of ocean water as it warms; melting of mountain glaciers worldwide; and melting of polar ice sheets in Greenland and Antarctica.

The MFE website states it's not possible to make a 'best estimate' of what future sea-level rise will be.

"Instead, plausible futures are best explored using a range of scenarios of future global greenhouse gas emissions that have been developed by climate change researchers for the IPCC."

Under all scenarios, the report says sea levels will continue to rise during the 21st century and beyond, and the rate of increase will very likely be faster than in the past few decades.

Projections show sea levels around New Zealand expected to rise between 30cm and 100cm this century.

Nearly 170,000 private and publicly-owned buildings sat within 3m of the mean high water spring, according to the most recent national assessment. This exposed them not just to sea level rise, but also storm-tide and wave flooding that could reach 1-2m.

Estimated cost of replacing all those structures was $52 billion.

Local Government's Role

Western Bay of Plenty District Council mayor Garry Webber said planning for sea level rise is high priority.

"You can put your head in the sand and say it's not gonna happen, but you just gotta look at trends over the last 15 or 20 years that something's happening to our environment."

Webber said finding solutions is a fundamental government responsibility. He points to a report published January 31by Local Government New Zealand (LGNZ) showing as much as $14 billion worth of council infrastructure is threatened by rising seas.

The LGNZ report found $2.7b of roading, three waters (drinking, storm and wastewater) and building infrastructure at risk from as little as half a metre rise in sea level. A one-metre rise put $5.1b of council assets at risk, while a three-metre rise risks $14.1b.

Western Bay of Plenty District Council group manager policy, planning and regulatory services Rachael Davie said council has already mapped coastal erosion and inundation (also known as storm surge) hazards for properties along the open coast at Waihi Beach and Pukehina. WBOPDC is also mapping hazards for properties along the Tauranga Harbour, including Matakana Island and its estuaries.

"Council will also need to identify these same hazards for the Maketu and Little Waihi estuaries in the near future."

LGNZ president Dave Cull said many councils were already experiencing the impact of sea level rise, especially in the Bay of Plenty, the West Coast, South Dunedin and Hawke's Bay.

"Using sea level rise scenarios that are based on the best local and international scientific advice, our research paints a really stark picture for local communities. That's not even factoring in the total value of assets at risk from sea level rise, which skyrockets when you start factoring things that sit on top of this infrastructure, like highways, homes, businesses, office buildings, hospitals, factories and schools."

LGNZ recommended central and local government jointly form a national adaptation fund to ensure costs were shared equally.

Insurance Council of New Zealand chief executive Tim Grafton said the LGNZ report only showed the 'tip of the iceberg'.

"We believe the full cost of exposure to central government and private sector property will be in the tens of billions of dollars."

Grafton says the more we spend reducing risks now, the less impact consumers will see in the future.

LGNZ vice president and Bay of Plenty Regional councillor Stuart Crosby (also former mayor of Tauranga) said a lot of work has been done around natural hazard issues the past couple years.

"The next conversation is who's going to pay, and clearly local government on its own or regional government cannot pay to either mitigate to protect these assets or relocate these assets."

Community members question Crosby about the wisdom of building in certain areas, he said.

"Papamoa East is an example. Should we be building all the way down there on the sand dunes, knowing about climate change, knowing about storm surge, liquefaction, all these issues?"

While much of Papamoa has been consented and built, new areas such as Te Tumu, to the immediate southeast, are still in planning stages. The development is projected to house more than 15,000 people when completed.

A 2017 TCC document states, "As a coastal area bounded by a river, Te Tumu is subject to potential natural hazards such as flooding, tsunami and liquefaction."

Council is working on risk assessments for sea level rise, coastal erosion, stormwater and groundwater. Construction is due to start in 2021.

Te Tumu Kaituna 14 Trust chairman Malcolm Short told Bay of Plenty Times Weekend long-term planning to reduce risks for future residents is the domain of Tauranga City Council, which sets minimum building levels.

"Those reports indicate to council where they should be putting the limitations and we just have to follow those limitations that they decree. It's pretty simple arithmetic, if the sea rise is predicted, for whatever it is the next 50 years, we make sure we're building above those lines with a safety margin."

Tauranga mayor Greg Brownless said the hope is ocean growth will be incremental, "... but you wouldn't want to go and open up a new subdivision somewhere that was predicted within 50 years was going to be a problem. If sea level rise is moderate, well, nobody has anything to worry about, but if it does accelerate, then we're going to have to treat it a lot more seriously."

By law, properties at risk of flooding or other hazards have warnings attached to their Land Information Memorandums (LIMs).

Brownless said LIM notations concern some homeowners, "... but many houses have got that. If council doesn't, and then later on, there's a problem, guess who gets blamed? Council. It's no use coming back 20 years later and saying, 'Oh, we didn't know' when council has put a notice on a title."

Brownless said he'd have no problem living by the water. "Life is full of risks. It's also fair to say that people increasingly are trying to put that risk onto someone else. You can't have it both ways."

Realty Services CEO Simon Anderson said anyone who cares about our coastline worries about swelling seas. Yet the pull of coastal living is strong.

"If you look at some of the prices paid for our waterfront over the last 12-18 months, you'd have to say there's either a lot of courage, or a real desire because those prices have not flattened, they've continued to go up."

Anderson points to sales of $5m and $6m homes on Oceanbeach Rd in Mount Maunganui the past year as proof.

Hard Calls and Hindsight

It's not only rising seas forcing tough calls; inland flood events have also impacted our neighbours. The BOP Regional Council last year adopted a plan change that will force residents of 34 properties (16 of them with homes) in high risk areas to leave by March 31, 2021.

A photo showing the aftermath of flooding in Matata in 2005./Photo: File

The decision follows torrential rains in 2005 which washed boulders through the Awatarariki stream, causing more than $20m in damage. After years of study, plans to build a dam were scrapped.

Homeowners say the Whakatane District Council has offered to buy out their homes at far less than market value. The council website states the risk of future debris flows is now far better understood. "... information provided by GNS indicates that a debris flow from the Awatarariki catchment can be expected every 50-150 years. Climate change is likely to increase the frequency of extreme weather events, which in turn is likely to increase the likelihood of debris flows from the catchment."

Western BOP mayor Garry Webber said many places exist in New Zealand where people have built on what are now considered flood plains or in areas susceptible to natural hazards.

"We've got parts in the district now where the insurance companies are saying, this is the level of risk, this is what your premiums are; you're asking landowners to make hard decisions."

That's why Webber said we need a national approach. "You accept it's going to happen and whether, how do we get between now and 50 years out."

He said much of our existing coastal housing stock could not be built, according to today's standards.

"Unfortunately, when you look at Waihi Beach and Pukehina, Whakatane, Ohope and around the coast, right 'round New Zealand, a lot of people want to live close to beaches, close to rivers, but now it's coming home that maybe some of those decisions in hindsight, we could've been a little better at."

With local elections in October, Webber said ratepayers and candidates must consider how to best protect future generations.

"And if you're not taking into consideration the impact of climate change in a lot of your decision-making, then you gotta ask the question, are you in the right space? We have to address this, and we have to address it sooner rather than later."

Central Government's Role

Climate Minister James Shaw said evidence in LGNZ's report reinforces central Government's resolve around work to address climate change and limit sea level rise. He said Government planned to establish a National Climate Change Risk Assessment system to help communities.

"That work will also incorporate consideration of the very difficult issue of how we spread the financial burden of climate change impacts."

The Resource Management Act (RMA) was amended in 2017 to require councils to manage significant risks from natural hazards as a matter of national importance.

Maori Assets Threatened

Māori are among groups most vulnerable to climate change, according to a 2017 government study. The report said there has been more heavy rainfall, flooding, erosion and landslides in the hills causing sedimentation of waterways on the coast since 2005. Among at-risk assets are urupā, or Maori burial sites.

A rāhui is in place at a Maketu beach after bones from a historic urupā were swept away following a landslide last month./Photo: File

In Maketu, a landslide last month on the eastern side of Okurei Point swept bones from a historic urupā into the sea. A six-week rāhui was placed on January 14, which ensures no one will collect kaimoana or other food from the beach and surrounding areas.

Te Runanga iwi manager Maria Horne told the Bay of Plenty Times Weekend historical bones are still surfacing, and whether the rāhui is extended will depend on if iwi members feel they've collected everything and performed the appropriate service to rebury bones.

"With the water and hard rain that comes down, and after weather where we don't have any rain, it makes our land more subject to erosion."

Horne says kaumatua have been considering relocating the marae, which is exposed to flooding from king tides.

"Our marae's located close to the Maketu estuary and while we don't have to do anything yet, the old people have been talking about effects of climate change on the marae location."

"We have our cemetery on Motuopae Island in the middle of Waikareao Estuary. Any dramatic sea level rise will affect us."

No Regrets

At Pukehina Beach, Paora Maxwell points out a dune marker erected in 2008. It indicates sand levels are roughly the same at this spot as they were 10 years ago. According to the regional council, dunes mitigate natural hazard risks. The sand height reassures Maxwell.

"The only thing that worries me is more extraordinary weather events. That's what's impacted on my property since I've been here. The joy of living on the beach far outweighs any concern I have about a potential one-metre rise in sea levels."

A dune marker at Pukehina Beach from 2008 indicates sand height./Photo: George Novak